From the Microsoft Knowledge Base Article KB 937930, You may be unable to switch between displays on a portable computer that is running Windows XP.
The article is listed as applying to Microsoft Windows XP Professional, not to Microsoft Windows XP Professional with Service Pack 2. So, this may be a moot point for our College Enterprise machines. But I found it interesting that the article lists the "wait for a full minute before you try to switch displays" as a workaround.
If you have this issue on your machine, you can at least try that.